Rainer Dahms

Research Interests

Dr. Dahms completed his PhD in aerospace and mechanical engineering from RWTH Aachen University, Germany in 2010 under the supervision of Prof. Dr.-Ing. Dr. h.c. Dr.-Ing. E.h. Norbert Peters. He then served as a postdoctoral fellow before he became a research scientist in 2012 at the Combustion Research Facility of Sandia National Laboratories in Livermore, California.  Dr. Dahms has expertise in the theory, simulation, analysis, and modeling of high-pressure reacting fluid flows that are dominated by multiphase phenomena, complex multicomponent mixtures, real-fluid transport and thermodynamics, turbulence, and their multi-scale interactions with elementary kinetics. His research focuses on the opportunities of mesoscale sciences for the development of theoretical-numerical models which seamlessly combine the governing dynamics at molecular and continuum scales.

Dr. Dahms developed a conceptual model for auto-ignition in high-pressure spray flames. It has led to the discovery of a previously unrecognized turbulence-chemistry-interaction phenomenon – a turbulent cool flame wave – which propagates through the flow field and greatly enhances the reactivity in yet unburnt regions. Then, ignition occurs where the combination of first-stage ignition delay, shorted by such cool flame waves, and subsequent delay until second-stage ignition becomes minimal.

He has also formulated a theory to predict the breakdown of classic two-phase theory and spray atomization at certain high-pressure conditions. Then, widely-accepted concepts such as vapor-liquid-equilibrium, true critical points of the mixture, immiscible interfaces, surface tension forces, and breakup processes come into question. Instead, the spray transitions to single-phase dense-fluid mixing.

He developed a model for the detailed treatment of deforming drop dynamics in dense spray regions. To-date, most models used for device-scale spray simulations neglect such physical complexities. The new model demonstrated significant improvements in predictions of drag forces, evaporation, and heating rates over calculations performed by contemporary frameworks.

He formulated a theory on the significance of spark-channel dynamics, non-spherical early flame-front propagation, and fuel properties, which include turbulent enthalpy fluctuations and Lewis number effects, in spray-guided spark-ignition processes. Based on this theory, he developed the spark-channel ignition monitoring model (SparkCIMM) to integrate such effects into turbulent combustion simulations.

Awards and Honors

  • U.S. DRIVE Advanced Combustion & Emissions Control (ACEC) Top Accomplishment, “Discovery of cool-flame wave enhances researchers understanding of Diesel auto-ignition processes,” 2016
  • Early-Career Lab Directed R&D Award, “High-fidelity models for fuel spray atomization,” Sandia Natl Labs, 2013-2015
  • U.S. DRIVE Advanced Combustion & Emissions Control (ACEC) Top Accomplishment, “Fundamental differences between Gasoline and Diesel fuel sprays revealed,” 2013
  • ILASS-Americas W.R. Marshall Award, Institute for Liquid Atomization & Spray Systems, 2012
  • Sandia Labs Accomplishments 2012, “Engineering Sciences – Supercritical Fuel Injection,” 2012
  • Borchers-Badge of Distinction, Ph.D. thesis, RWTH Aachen University, 2011
  • European Da Vinci Silver Medal, “Analyzing spark ignition phenomena in spray-guided gasoline engines,” European Research Community on Flow, Turbulence and Combustion (ERCOFTAC) 2010
  • New spark ignition model “SparkCIMM” presented at Princeton University Combustion Summer School, 2010
  • Intl. Distinguished Paper Award, The Combustion Institute, 2009

Links

  • Sandia research: http://crf.sandia.gov/combustion-research-facility/reacting-flow/
  • Google scholar: https://scholar.google.com/citations?hl=en&user=e5hu8UUAAAAJ

Selected Publications

  • R. N. Dahms, G. A. Paczko, S. A. Skeen, and L. M. Pickett, “Understanding the ignition mechanism of high-pressure spray flames,” Proc. Combust. Inst. 36 (2016), doi:10.1016/j.proci.2016.08.023
  • R. N. Dahms and J. C. Oefelein, “The significance of drop non-sphericity in sprays,” Int. J. Multiphase Flow 86:67-85 (2016), doi: 10.1016/j.ijmultiphaseflow.2016.07.010.
  • R. N. Dahms, “Understanding the breakdown of classic two-phase theory and spray atomization at engine-relevant conditions,” Phys. Fluids 28:042108 (2016), doi:10.1063/1.4946000.
  • R. N. Dahms, “Gradient Theory simulations of pure fluid interfaces using a generalized expression for influence parameters and a Helmholtz energy equation of state for fundamentally consistent two-phase calculations,” J. Colloid Interface Sci. 445:48–59 (2015), doi:10.1016/j.jcis.2014.12.069.
  • R. N. Dahms and J. C. Oefelein, “Liquid jet breakup regimes at supercritical pressures,” Combust. Flame 162:3648–3657 (2015), doi:10.1016/j.combustflame.2015.07.004.
  • T. D. Fansler, D. L. Reuss, V. Sick, and R. N. Dahms, “Combustion instability in spray-guided stratified-charge engines: A review,” Int. J. Engine Res. 16:260–305 (2015),
    doi:10.1177/1468087414565675.
  • R. N. Dahms, J. C. Oefelein, A. Jasper, J. Manin, and L. M. Pickett, “The breakdown of classic spray atomization at device-relevant conditions,” Invited Seminar, Massachusetts Institute of Technology, Sept. 23 (2015)
  • R. N. Dahms and J. C. Oefelein, “Development of high-fidelity models for liquid fuel spray atomization and mixing processes in transportation and energy systems,” SNL Unlimited Release Report SAND-2015-3314, 2015.
  • R. N. Dahms and J. C. Oefelein, “Atomization and dense-fluid breakup regimes in liquid rocket engines,” Journal of Propulsion and Power 31:1221–1231 (2015), doi:10.2514/1.B35562.
  • R. N. Dahms and J. C. Oefelein, “Non-equilibrium gas-liquid interface dynamics in high-pressure liquid injection systems,” Proc. Combust. Inst. 35: 1587–1594 (2015), doi:10.1016/j.proci.2014.05.155.
  • R. N. Dahms and J. C. Oefelein, “Transition between two-phase and single-phase interface dynamics in liquid injection processes at supercritical pressures,” Invited Seminar, Edwards Air Force Research Laboratory, Feb. 20 (2013).
  • R. N. Dahms and J. C. Oefelein, “On the transition between two-phase and single-phase interface dynamics in multicomponent fluids at supercritical pressures,” Phys. Fluids 25, 092103 (2013), doi:10.1063/1.4820346.
  • R. N. Dahms, J. Manin, L. M. Pickett, and J. C. Oefelein, “Understanding high-pressure gas-liquid interface phenomena in diesel engines,” Proc. Combust. Inst. 34:1667–1675 (2013), doi:10.1016/j.proci.2012.06.169.
  • R. N. Dahms, M. C. Drake, T. D. Fansler, R. O. Grover, and A. S. Solomon, “Detailed simulations of stratified ignition and combustion processes in a spray-guided gasoline engine using the SparkCIMM/G-equation modeling framework,” SAE Int. J. Engines 5:141–161 (2012), doi:10.4271/2012-01-0132.
  • R. N. Dahms, M. C. Drake, T.-W. Kuo, and N. Peters, “Understanding ignition processes in spray-guided gasoline engines using high-speed laser imaging techniques & the extended spark-ignition model SparkCIMM – Part A: Spark channel processes and the turbulent flame front propagation,” Combust. Flame 158:2229–2244 (2011), doi:10.1016/j.combustflame.2011.03.012.
  • R. N. Dahms, M. C. Drake, T. D. Fansler, T.-W. Kuo, and N. Peters, “Understanding ignition processes in spray-guided gasoline engines using high-speed imaging techniques & the extended spark-ignition model SparkCIMM – Part B: Importance of molecular fuel properties in early flame front propagation,” Combust. Flame 158:2245–2260 (2011), doi:10.1016/ j.combustflame.2011.04.003.
  • R. N. Dahms, C. Felsch, O. Röhl, and N. Peters, “Detailed chemistry flamelet modeling of mixed-mode combustion in spark-assisted HCCI engines,” Proc. Combust. Inst. 33:3023–3030 (2011), doi:10.1016/j.proci.2010.08.005.
  • R. N. Dahms, M. C. Drake, T. D. Fansler, T.-W. Kuo, A. M. Lippert, and N. Peters, “Modeling ignition phenomena in spray-guided spark-ignited engines,” Proc. Combust. Inst. 32:2743–2750 (2009), doi:10.1016/j.proci.2008.05.052.
  • R. N. Dahms, N. Peters, D. W. Stanton, Z. Tan, and J. Ewald, “Pollutant formation modeling in natural gas SI engines using a level set based flamelet model,” Int. J. Engine Res. 9:1–14 (2008), doi:10.1243/14680874JER02107.